There have been known a variety of spherical fine particles, both inorganic and organic, and they are in use for a broad range of applications. Inorganic spherical fine particles are generally hard but have no elasiticity, what's more, they have a disadvantage of being poor in resistance to chemicals (such as acids and alkalis) and organic solvents. There have been known organic spherical fine particles which are made of epoxy resin, acrylic resin, polyester-polyether urethane resin (*), nylon resin, polyethylene resin, polypropylene resin, phenolic resin, or amino resin. These organic spherical fine particles, unless crosslinked, are poor in toughness, elastic properties, recovery, solvent resistance, heat resistance, and chemical resistance. When crosslinked, they are partly exempt from the above-mentioned disadvantages of inorganic spherical fine particles and uncrosslinked organic spherical fine particles; but they still do not meet all of the requirements for mechanical characteristics (such as toughness and elastic properties) and resistance to chemicals (acids and alkalis) and organic solvents and weathering. FNT (* See Japanese Patent Publication No. 8116/1975, Japanese Patent Laid-open No. 611/1990, and U.S. Pat. No. 4,783,502.)
The above-mentioned inorganic or organic spherical fine particles are dispersed in the resin for binder and are used as a component of a coating composition which gives rise to a coating film having a leatherlike or velvetlike finish. There have been proposed many kinds of such coating compositions. Unfortunately, the performance of coating compositions are not improved enough because of the above-mentioned disadvantages involved in inorganic and organic spherical fine particles. Therefore, they give rise to a filmy product (formed by molding into film) and a sheet product (formed by application to a substrate) which do not have the desired performance. In addition, the abovementioned spherical fine particles are used as a component of a peelable pressure-sensitive adhesive. In this case, too, the peelable pressure-sensitive adhesive is not good enough in adhesion, peelability, durability, and weathering because of the above-mentioned disadvantages involved in spherical fine particles.
The present invention was completed in view of the foregoing. Accordingly, it is an object of the present invention to provide crosslinked spherical fine particles having outstanding mechanical characteristics (such as toughness and elastic properties) and good resistance to chemicals (acids and alkalis) and organic solvents and weathering. The crosslinked spherical fine particles are useful as follows; a filler, delustering agent, and reinforcing agent for paints, plastics, rubber and so on; a spacer for liquid-crystal display units; a carrier or toner for electrostatic duplicators; and a filler for cosmetics and toothpaste.
It is another object of the present invention to provide a process for producing crosslinked spherical fine particles having the above-mentioned characteristic properties.
It is further another object of the present invention to provide a coating composition containing said crosslinked spherical fine particles and articles based on said coating composition. The coating composition gives rise to a leatherlike or velvetlike coating film having a excellent appearance and feel owing to the characteristics of the crosslinked spherical fine particles. The articles include a filmy product which is formed by molding the coating composition into film, a sheet product which is formed by application of the coating composition onto one side or both sides of a substrate, and an adhesive film or sheet which is formed by providing one side of said filmy product or sheet product with an adhesive layer.
It is still further another object of the present invention to provide a peelable pressure-sensitive adhesive formed by incorporating a pressure-sensitive adhesive with said crosslinked spherical fine particles as a component to improve peelability, and also to provide a peelable pressure-sensitive adhesive article formed by applying said peelable pressure-sensitive adhesive onto one side of a sheetlike substrate.
Other and further objects, features and advantages of the invention will appear more fully from the following description.